1. Field of the Invention
The present invention generally relates to synthesizers and, more particularly, is directed to a raster distortion correcting signal synthesizer suitable for use in a monitor receiver or the like.
2. Description of the Prior Art
As a raster distortion correcting signal synthesizer used in a monitor receiver or the like, there has been proposed an apparatus which generates a correcting signal for correcting the raster distortion such as a sawtooth wave signal or a parabolic wave signal or the like in accordance with a count value of a horizontal synchronizing (sync.) signal. However, the proposed conventional synthesizer or apparatus is constituted by analog circuits, so-called hard logic, and digital adder-subtracters.
The demand for accuracy of an image with respect to the distortion has been increasing according to the tendency of flattening and enlarging a cathode ray tube (CRT), so that a high-order raster distortion correcting signal has been required. However, when the high-order raster distortion correcting signal is generated by the conventional synthesizer employing the analog circuits and digital adder-subtracters, it has been difficult to obtain sufficient accuracy of the image.
Further, in case of producing a multistandardized television receiver having the conventional synthesizer employing the analog circuits and digital adder-subtracters, it is required to arrange the circuit configurations for every system or receiver. In this case, it is further required to store parameters required for the adjustments for every system, so that a memory or the like for storing the parameters is required, resulting in the circuit configurations being enlarged.